The present invention is directed toward a fluid delivery system and more particularly to a safety system that automatically closes one or more valves in the fluid delivery system in the event that an eminent rupture is sensed.
In the past, various techniques have been used for transferring hazardous liquids or fluids between two tanks such as, for example, between a portable roadway vehicle tank and a fixed storage tank. This is normally done utilizing flexible hoses or the like. Since the release of hazardous materials could result in a life-threatening situation, special precautions are taken to ensure that little if any of the liquid or fluid is released to the ground or atmosphere during transfer of the material along the flexible hose. While the flexible hose may be only a portion of the fluid transmission system between the tanks, is an important link in the transfer of fluids to or from a portable tank, such as mounted on a roadway vehicle.
A number of safety systems have been proposed in the past to limit or control spillage of hazardous liquids or fluids in the event of a malfunction. One prior art system marketed by Smart-Hose Technologies, Inc. utilizes a cable in compression within the hose which normally unseats valve members located at each end of the cable. In the event of hose rupture or separation, the valve members are released to stop the flow of product in both directions. The cable acts as a spring to maintain the valves off of their seats, and the separation of the hose releases the biasing force of the valves which then move to the closed position. Variations of the smart hose system are described in U.S. Pat. Nos. 5,357,998; 6,260,569 and 6,546,947.
While the Smart-Hose systems have been beneficial, they are not always entirely satisfactory. It is, for example, difficult to verify the operational integrity of the system since there is limited ability to check whether the internal cable is in proper compression. Furthermore, during handling and coiling of the hose, special care must be taken not to bend the hose or the cable or the cable will lose its ability to hold the valves open. More importantly, the valves will not close until and unless there is an almost entire rupture or separation of the hose. A partial tear or rupture in the hose wall may result in a significant amount of leakage or spillage of the hazardous material without the valves closing as the cable may continue to operate to hold the valves in their open position.
Other systems have been devised which are intended to close shutoff valves along the length of a flexible hose based upon a drop in monitored pressure (of the hazardous fluid being transported) when the hose breaks. See, for example, U.S. Pat. No. 6,308,753. However, pressure monitoring systems for automatically closing valves at the ends of a flexible hose have various reliability concerns. Near the completion of the unloading operation when the liquid level gets low in the tank, the system becomes unreliable because of liquid and vapors entering the pump in a random fashion which can cause the valves to shut off when not necessary.
With such prior art systems, the device could be manually overridden when the tank is near empty to prevent the premature trip of the shutoff valve. A separate problem, however, involves determining when the tank is near empty since the unloading time is a function of pressure and pump condition, and typically lasts for over 30 minutes. Even if one could determine when to begin the override, this will create a situation where the operator could override the device at will and defeat the purpose of a system which automatically closes the valves at the ends of the hose to prevent spillage. Moreover, even after a tank is empty, the pump is typically run for several minutes to push most of the liquid in the hose into the receiving vessel. Running a pump in this situation will thus always actuate a device that is triggered by low pressure and manual override options do not practically solve the problem.
Most significantly, however, is the fact that even such low pressure monitoring systems do not prevent the spillage of hazardous fluids or liquids. This is due to the fact that the low pressure of the transported fluid is not sensed until the hose has ruptured and a significant amount of hazardous material has already been released. Furthermore, even after the valves are closed, material remaining within the hose can be released.
As a result, a need exists for a fluid delivery system that is capable of sensing a rupture before it occurs and closing one or more valves in the fluid delivery system in order to essentially totally prevent spillage of hazardous material.